Table of contents

1. A Review of General Chemistry5h 5m
2. Molecular Representations1h 14m
3. Acids and Bases2h 46m
4. Alkanes and Cycloalkanes4h 17m
5. Chirality3h 39m
6. Thermodynamics and Kinetics1h 22m
7. Substitution Reactions1h 48m
8. Elimination Reactions2h 30m
9. Alkenes and Alkynes2h 9m
10. Addition Reactions3h 19m
11. Radical Reactions1h 58m
12. Alcohols, Ethers, Epoxides and Thiols2h 42m
13. Alcohols and Carbonyl Compounds2h 17m
14. Synthetic Techniques1h 26m
15. Analytical Techniques:IR, NMR, Mass Spect7h 3m
16. Conjugated Systems6h 13m
17. Ultraviolet Spectroscopy51m
18. Aromaticity2h 34m
19. Reactions of Aromatics: EAS and Beyond5h 1m
20. Phenols55m
21. Aldehydes and Ketones: Nucleophilic Addition4h 56m
22. Carboxylic Acid Derivatives: NAS2h 51m
23. The Chemistry of Thioesters, Phophate Ester and Phosphate Anhydrides1h 10m
24. Enolate Chemistry: Reactions at the Alpha-Carbon1h 53m
25. Condensation Chemistry2h 9m
26. Amines1h 43m
27. Heterocycles2h 0m
28. Carbohydrates5h 53m
29. Amino Acids4h 20m
30. Peptides and Proteins2h 42m
31. Catalysis in Organic Reactions1h 30m
32. Lipids 2h 50m
33. The Organic Chemistry of Metabolic Pathways2h 52m
34. Nucleic Acids1h 32m
35. Transition Metals6h 14m
36. Synthetic Polymers1h 49m

21. Aldehydes and Ketones: Nucleophilic Addition

Nitrile to Ketone

Organic Chemistry

21. Aldehydes and Ketones: Nucleophilic Addition

Nitrile to Ketone

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2:30 minutes

Problem 27

Textbook Question

A ketone can be prepared from the reaction of a nitrile with a Grignard reagent. Describe the intermediate formed in this reaction, and show how it can be converted to a ketone.

Verified step by step guidance

The reaction begins with the nucleophilic attack of the Grignard reagent (R-MgX) on the carbon atom of the nitrile group (R'-C≡N). This carbon is electrophilic due to the polarization of the triple bond between carbon and nitrogen.

The nucleophilic attack results in the formation of an intermediate imine salt. The structure of this intermediate can be represented as R'-C=N⁻-MgX, where the nitrogen atom carries a negative charge and is bonded to the magnesium ion.

The imine salt intermediate is then hydrolyzed in the presence of water or an acidic workup. During hydrolysis, the imine group (C=N⁻) is converted into a carbonyl group (C=O).

The hydrolysis step involves protonation of the nitrogen atom, followed by the cleavage of the C=N bond and the addition of water to form a ketone (R'-C=O-R).

The final product of the reaction is a ketone, where the alkyl group from the Grignard reagent (R) is attached to the carbonyl carbon of the original nitrile (R'-C≡N).

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Grignard Reagents

Grignard reagents are organomagnesium compounds that act as nucleophiles in organic reactions. They are formed by the reaction of an alkyl or aryl halide with magnesium metal in anhydrous ether. In the context of the reaction with nitriles, Grignard reagents attack the electrophilic carbon of the nitrile, leading to the formation of a new carbon-carbon bond.

Nitrile Intermediate

When a Grignard reagent reacts with a nitrile, it forms an intermediate known as an imine or a ketimine, depending on the structure of the nitrile. This intermediate contains a carbon-nitrogen double bond and is crucial for the subsequent transformation into a ketone. The imine can be hydrolyzed to yield the corresponding ketone upon treatment with water or an acid.

Hydrolysis of Imines

Hydrolysis of imines involves the addition of water to the imine intermediate, leading to the cleavage of the carbon-nitrogen double bond. This reaction typically requires an acid catalyst to facilitate the process. The result is the formation of a ketone and the release of ammonia, completing the conversion from the nitrile to the ketone through the imine intermediate.

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